The aims of this proposal are to study paracrine regulation arising from loccellular interactions in bone tissue and to define the role cAMP in bone resorption. These studies will use a model system of cultured osteoclastic and osteablastic cells established in this laboratory Purified osteoclasts have been otained by permitting freshly isolated bone cells to attach to polystyrene in the presence of OB cell conditioned medium which appears to both promote OC cell attachment and inhibit that of OB cells. These OC cells, highly enriched for acid phosphatase activity, are incapable of responding to PTH with increased hyaluronate synthesis, in contrast to osteoclasts in situ in bone tissue, and in mixed bone cell populations. The capacity to express this response to PTH was restored however upon coculture of the purified osteoclasts with osteoblasts or with dialyzed osteoblast conditioned medium. We plan to purify and characterize the OB derived factors that regulate OC and OB cell attachment and PTH response in OC cells. Purification will be attempted from OB cells and conditioned medium using HPLC isocratic chromatography. We also wish to examine the mechanism of action of these OB cell derived factors and possible hormonal control of their synthesis and secretion. If these OB cell derived factors are important regulatory mechanisms in vivo in bone, then aberrations in their synthesis may underlie some metabolic bone diseases and purification and identification of these factors may have clinical importance. With regard to the role of cAMP in bone resorption, we have observed that both PGE2 and PTH induce cAMP in purified osteoclasts but only PGE2 can induce hyaluronate synthesis in the absence of OB cells. We plan to compare PGE2 and PTH stimulation of soluble and particulate protein kinase and phosphorylation of proteins in OC cells to try to correlate specific cAMP induced changes with induction of the bone resorption marker activity.